October 2022
Beginner to intermediate
390 pages
7h 5m
Chinese
Content preview from Perl语言入门（第8版）
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目录操作
｜
241
Perl
内置的
glob
并非唯一选择。我们可以用
File::Glob
模块提供各式兼容和
扩展的文件名通配。
文件名通配的隐式语法
虽然我们一直在介绍文件名通配，也介绍了
glob
操作符的用法，可在许多进行文件
名通配处理的程序里你可能完全看不到
glob
这个词。为什么呢？那是因为大部分过
去写的程序都是在
glob
操作符出现之前写的。它们使用尖括号语法来调用此功能，
看起来就跟读取自文件句柄差不多：
my @all_files = <*>; #
效果和这样的写法完全一致：
my @all_files = glob "*";
Perl
会把尖括号内出现的变量替换成它的值，类似于双引号内字符串的变量内插，这
表示在进行文件名通配之前，
Perl
会把变量展开为它的当前值：
my $dir = '/etc';
my @dir_files = <$dir/* $dir/.*>;
此处，因为
$dir
会被展开成它当前的值，所以最终会取得指定目录下的所有文件，
不管文件名称是以点号开头的还是不以点号开头的。
这样说来，假如尖括号既表示从文件句柄读取又代表文件名通配操作，那
Perl
又是如
何判断取舍的呢？嗯，因为合理的文件句柄必须是严格意义上的
Perl
标识符，所以如
果尖括号内是满足
Perl
标识符条件的，就作为文件句柄来读取；否则，它代表的就是
文件名通配操作。比如：
my @files = <FRED/*>; #
文件名通配操作
my @lines = <FRED>; #
从文件句柄读取 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.